| 摘要 |
A MOS FET (Q1) of a switching circuit (1) is turned on/off, controlled by a pre-drive circuit (2) via a pulse transformer (T). For switching on, a drive transistor (Q2) on the primary side (P1) of the pulse transformer is turned on, which generates a voltage on the secondary side (51). This charges the gate (G) of the MOS FET (Q1) to the positive side and turns on the switch. For switching off, the drive transistor (Q2) is turned off and the gate (Q) is discharged via a current flow (IE). The MOS FET (Q1) is switched off when the gate voltage becomes zero. The gate voltage further drops until it reaches a negative level determined by a zener diode (ZD3), when another FET (Q3) is switched off, further current flow (IE) is prevented. |
